Read the forums. While its not been confirmed that it will, as Frontier already have Elite on Steam it seems very likely to be. However, they certainly wont release it on Steam until its finished and thats not for some time yet.
As a benchmark, Elite Dangerous went on Steam about 3 months after it's initial release so I wouldnt expect to see it before then, however, the fact that this game is likely to take advantage of the Steam workshop means we can hope for a Steam release on or close to the main full release.